Cardiac rhythm management (CRM) devices are well known in the art. They include implantable pacemakers which provide stimulation pulses to a heart to cause a heart, which would normally or otherwise beat too slowly or at an irregular rate, to beat at a controlled normal rate. They also include defibrillators which detect when the atria and/or the ventricles of the heart are in fibrillation and apply cardioverting or defibrillating electrical energy to the heart to restore the heart to a normal rhythm. Implantable cardiac devices may also include the combined functionalities of a pacemaker and a defibrillator.
Implantable cardiac stimulation devices sense cardiac activity for monitoring the cardiac condition of the patient in which the device is implanted. By sensing the electrical cardiac activity of the patient, the device is able to provide cardiac stimulation therapy when it is required. The sensed cardiac activity may also be used to monitor for and detect other cardiac conditions such as cardiac ischemia.
It has been recognized that knowledge of electrical activity of the heart may provide significant insight into the existence of non-cardiac conditions such as hypoglycemia (low blood sugar levels) and hyperglycemia (high blood sugar levels). Such uses of sensed cardiac activity is disclosed in U.S. patent application Ser. No. 11/043,612, filed Jan. 25, 2005, entitled “System and Method for Distinguishing Among Cardiac Ischemia, Hypoglycemia and Hyperglycemia Using An Implantable Medical Device,” of Kil et al.
Those skilled in the art have thus recognized the possibility of detecting non-cardiac conditions using sensed cardiac electrical activity. The invention advances this recognition by using cardiac electrical activity to monitor for and detect renal failure.